Metal oxide (MO) semiconductor and thin-film transistor and application thereof

ABSTRACT

The present invention discloses a metal oxide (MO) semiconductor, which is implemented by respectively doping at least an oxide of rare earth element R and an oxide of rare earth element R′ into an indium-containing MO semiconductor to form an InxMyRnR′mOz semiconductor. According to the present invention, the extremely high oxygen bond breaking energy in the oxide of rare earth element R is used to effectively control the carrier concentration in the semiconductor, and a charge transportation center can be formed by using the characteristic that the radius of rare earth ions is equivalent to the radius of indium ions, so that the electrical stability of the semiconductor is improved. The present invention further provides a thin-film transistor based on the MO semiconductor and application thereof.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part-application of U.S.patent application Ser. No. 16/529,833, titled “OXIDE SEMICONDUCTORTHIN-FILM AND THIN-FILM TRANSISTOR CONSISTED THEREOF”, filed on Aug. 2,2019. US parent application Ser. No. 16/529,833 is a continuation ofPCT/CN2017/111109, filed on Nov. 15, 2017, and claims foreign priorityto Chinese patent application No. 201710229199.9, filed on Apr. 10,2017. The present application claims foreign priority to Chinese PatentApplication No. 201710229199.9, filed on Apr. 10, 2017 and ChinesePatent Application No. 202011314502.3, filed on Nov. 20, 2020, where arehereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to the field of semiconductormanufacturing, in particular, to materials and device structures usedfor manufacturing backboards of metal oxide (MO) semiconductor thin-filmtransistors in flat panel display and detector applications, and inparticular, to an MO semiconductor and a thin-film transistor andapplication thereof.

BACKGROUND

In a present metal oxide semiconductor system, indium ion (In³⁺) has arelatively large ion radius, which ensures its efficient carriertransport channel with a higher probability of orbital overlap in amulti-element metal oxide, and its 5s orbital is a main electrontransport channel. However, on the one hand, due to the lower bondbreaking energy of In—O after indium bonds with oxygen, a large numberof oxygen vacancy defects are present in pure indium oxide (In₂O₃)thin-films. Oxygen vacancy is the main reason for the stabilitydeterioration of metal oxide thin-film transistors. On the other hand,many lattice mismatches occur in indium oxide that forms a film byconventional sputtering. This makes the carrier mobility of thethin-film low, which limits its application in high-performancethin-film transistors. It is generally necessary to dope Ga³⁺ ions withthe same amount as In³⁺ ions to regulate the oxygen vacancy. Besides, toensure the performance uniformity of semiconductor devices, the MOsemiconductor thin-film needs to keep an amorphous thin-film structure.

Because the crystal structure of ZnO is quite different from that ofIn₂O₃ and that of Ga₂O₃, doping Zn ions with the same amount as In ionsin the thin-film can inhibit the crystallization of the material andkeep the amorphous structure of the thin-film. Therefore, IGZO(In:Ga:Zn=1:1:1 mol) is the most widely used MO semiconductor materialat present.

However, IGZO also has some problems: The addition of a large number ofGa³⁺ and Zn³⁺ ions greatly dilutes the concentration of In³⁺, therebyreducing the overlapping degree of 5s orbitals and lowering the electronmobility.

In addition, IGZO and other materials have a large number of trap statesnear the valence band. This leads to the generation of photo-inducedcarriers even if the illumination energy is lower than the band gap,resulting in the poor illumination stability of current MOsemiconductors.

SUMMARY

To overcome the shortcomings of the prior art, the present inventionprovides an MO semiconductor with relatively high mobility and strongillumination stability, which is implemented by using a new co-dopingstrategy, makes use of the special 4f electron orbital characteristicsof rare earth oxides, can control the carrier concentration and obtainan MO semiconductor with strong illumination stability while achievinghigher mobility in oxide films with high in ratio.

The new co-doping strategy according to the present invention is tointroduce oxide materials of rare earth element R and oxide materials ofrare earth element R′ with different functions into an MO containingindium, where the oxide of rare earth element R is a carrierconcentration control agent and the oxide of rare earth element R′ is alight stabilizer, that is, the oxide of rare earth element R′ is acharge transportation center, and its action principle is as follows:

The carrier concentration control agent is implemented based on thatYb²⁺ ions and Eu²⁺ ions in ytterbium oxide and europium oxide which areoxides of rare earth element R have full and half full 4f electronorbitals, respectively. Therefore, divalent ions in the oxide of rareearth element R have lower energy in the oxide than trivalent ions. Inan oxide semiconductor, when In³⁺ ions are substituted for doping, thecarrier concentration can be obviously reduced. In addition, the bondbreaking enthalpy changes (ΔHf298) of Yb—O and Eu—O are 715.1 kJ/mol and557.0 kJ/mol, respectively, which are much higher than the bond breakingenergy (360.0 kJ/mol) of In—O, thereby effectively controlling theoxygen vacancy concentration. In summary, with reference to the abovetwo characteristics, the introduction of the oxide of rare earth elementR can effectively control the oxygen vacancy of oxide semiconductorthin-films in a high In system. Because the ion radius of Yb²⁺ is lessthan that of Eu²⁺, it is more conducive to reducing the In—In distancein the oxide semiconductor, thereby keeping its better high mobilitycharacteristics.

The light stabilizer is implemented based on that the radius of rareearth ions of materials such as praseodymium oxide, terbium oxide,cerium oxide and dysprosium oxide of the oxides of rare earth element R′is equal to the radius of indium ions in indium oxide, and the electronstructure of 4f orbitals in the rare-earth ions and 5s orbitals of theindium ions can form an efficient charge transportation center, so as toimprove the electrical stability, and especially the stability underillumination.

A second object of the present invention is to provide a thin-filmtransistor including the MO semiconductor.

A third object of the present invention is to provide application of thethin-film transistor.

The present invention is implemented by using the following technicalsolution:

A metal oxide semiconductor is provided, where the metal oxidesemiconductor is implemented by respectively doping at least an oxide ofrare earth element R and an oxide of rare earth elements R′ into anindium-containing metal oxide MO—In₂O₃ semiconductor to form anIn_(x)M_(y)R_(n)R′_(m)O_(z) semiconductor material, where x+y+m+n=1,0.4≤x≤0.9999, 0≤y<0.5, 0.0001≤(m+n)≤0.2, m>0, n>0, and z>0.

That is, the MO semiconductor according to the present invention is acomposite semiconductor based on indium oxide, and two rare earth oxideswith different but complementary functions are introduced throughco-doping. Oxides of rare earth element R can be selected from ytterbiumoxide and europium oxide, which are used as a carrier concentrationcontrol agent. Yb²⁺ ions and Eu²⁺ ions in ytterbium oxide and europiumoxide are used, which have full and half full 4f electron orbitals,respectively. Therefore, divalent ions in the oxide of rare earthelement R have lower energy in the oxide than trivalent ions. In anoxide semiconductor, when In³⁺ ions are substituted for doping, thecarrier concentration can be obviously reduced. In addition, the bondbreaking enthalpy changes (ΔHf298) of Yb—O and Eu—O are 715.1 kJ/mol and557.0 kJ/mol, respectively, which are much higher than the bond breakingenergy (360.0 kJ/mol) of In—O, thereby effectively controlling theoxygen vacancy concentration. With reference to the above twocharacteristics, the introduction of the oxide of rare earth element Rcan effectively control the oxygen vacancy of oxide semiconductorthin-films in a high In system. Because the ion radius of Yb²⁺ is lessthan that of Eu²⁺, it is more conducive to reducing the In—In distancein the oxide semiconductor, thereby keeping its better high mobilitycharacteristics.

In addition, oxides of rare earth element R′ can be selected frompraseodymium oxide, terbium oxide, cerium oxide, and dysprosium oxide.In material selection, an efficient charge transportation center can beformed by using the electron structure characteristics of the 4forbitals in the rare-earth ions and the 5s orbitals of the indium ions.Under positive bias, the rare-earth ions are in a stable low-energystate. The thin-film has a high carrier concentration due to themodulation of Fermi level, which can effectively shield the carrierscattering effect caused by the transportation center, thereby having noobvious impact on electrical characteristics and the like of a device.Under negative bias, the electron orbitals of rare-earth element 4f arecoupled with the 5s orbitals of indium, and the rare-earth ions are inan unstable activated state. On the one hand, this increases theoff-state current of the device and enhances the scattering effect oncarriers, which makes the subthreshold swing of the device slightlyincrease; on the other hand, when photo-induced carriers are excited bysuitable light, photo-induced electrons are quickly “captured” by theactivated transportation center, and the photo-induced carriers andionized oxygen vacancies recombine in the form of non-radiativetransition through their coupling orbitals; in addition, the activationcenter resumes the activated state. Therefore, the transportation centercan provide a fast recombination channel of the photo-induced carriersand prevent their impact on I-V characteristics and stability. Thestability of MO semiconductor devices under illumination is greatlyimproved.

Further, the oxide of the rare earth element R is a carrierconcentration control agent; and the oxide of the rare earth element Ris one or a combination of ytterbium oxide and europium oxide.

Further, the oxide of the rare earth element R′ is a light stabilizer,and the oxide of the rare earth element R′ is one material selected frompraseodymium oxide, terbium oxide, cerium oxide and dysprosium oxide ora combination of any two or more thereof.

Further, in MO, M is one material selected from Zn, Ga, Sn, Ge, Sb, Al,Mg, Ti, Zr, Hf, Ta, and W or a combination of any two or more thereof.

Further, the MO semiconductor is prepared into a film by using any oneof a physical vapor deposition process, a chemical vapor depositionprocess, an atomic layer deposition process, a laser deposition process,a Reactive-Plasma Deposition (RPD) process and a solution method.

The second objective of the present invention is implemented by adoptingthe following technical solution:

A thin-film transistor, including a gate electrode, an active layer, aninsulating layer located between the gate electrode and the activelayer, a source electrode and a drain electrode electrically connectedto both ends of the active layer respectively, and a spacer layer, wherethe active layer is the foregoing MO semiconductor.

That is, the present invention further provides the thin-film transistorcomposed of the active layer prepared on the basis of the MOsemiconductor. The MO semiconductor is implemented by introducing anoxide of rare earth element R and an oxide of rare earth element R′ withdifferent functions into an MO containing indium, where the oxide of therare earth element R is used as a carrier concentration control agentwhile the oxide of the rare earth element R′ is used as a lightstabilizer, so that the semiconductor can keep good high mobilitycharacteristics and improve its electrical stability, especially itsstability under illumination.

Further, the spacer layer is one layer structure selected from a siliconoxide thin-film, a silicon nitride thin-film and a silicon oxynitridethin-film prepared by plasma-enhanced chemical vapor deposition or alaminated structure composed of any arbitrary two or more thereof.

The third object of the present invention is implemented by adopting thefollowing technical solution:

Application of the thin-film transistor in a display panel or adetector.

Compared with the prior art, the present invention has the followingbeneficial effects.

According to the present invention, a new co-doping strategy is adopted,two rare earth oxide materials with different functions are introducedinto an indium-based MO, so that the carrier concentration iscontrolled, and good illumination stability of a device is achieved,which provides a new idea for the realization of high-performance MOsemiconductor materials in the future.

According to the present invention, at least an oxide of rare earthelement R and an oxide of rare earth element R′ are introduced into anindium-containing MO to form an MO semiconductor, where the oxide of therare earth element R is controlled as a carrier and the oxide of therare earth element R′ functions to enhance illumination stability, so asto effectively control the carrier concentration in the oxidesemiconductor by using the extremely high oxygen bond breaking energy inthe oxide of the rare earth element R. In addition, an efficient chargetransportation center can be formed by using the characteristics thatthe radius of rare-earth ions is equal to that of indium ions in indiumoxide, and the electron structure of 4f orbitals in the rare-earthelement R′ ions and 5s orbitals of the indium ions, so as to improve theelectrical stability, and especially the stability under illumination.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic structural diagram of a thin-film transistor ofexample 13 and example 14;

FIG. 2 is a schematic structural diagram of a thin-film transistor ofexample 15, example 16 and example 17;

FIG. 3 is a schematic structural diagram of a thin-film transistor ofexample 18;

FIG. 4 is a device transfer characteristics and photo-currentcharacteristic diagram of example 13;

FIG. 5 is a device transfer characteristics and photo-currentcharacteristic diagram of example 14;

FIG. 6 is a device transfer characteristics and photo-currentcharacteristic diagram of example 15;

FIG. 7 is a device transfer characteristics and photo-currentcharacteristic diagram of example 16;

FIG. 8 is a device transfer characteristics and photo-currentcharacteristic diagram of example 17; and

FIG. 9 is a device transfer characteristics and photo-currentcharacteristic diagram of example 18.

Reference numbers in the figures: 01. substrate; 02. buffer layer; 03.channel layer; 04. insulating layer; 05. gate electrode; 06. spacerlayer; 07-1, source electrode; 07-2. drain electrode; 08. etch-stoplayer.

DESCRIPTION OF EMBODIMENTS

The present invention is further described below with reference to theaccompanying drawings and specific embodiments. It should be noted thatall embodiments described below or all the technical features can bearbitrarily combined to form new embodiments, provided that no conflictoccurs.

The following are specific embodiments of the present invention, and theraw materials, equipment, etc. used in the following embodiments can beobtained through purchase except for special restrictions.

Example 1: Praseodymium Oxide- and Europium Oxide-Doped InSnZnOSemiconductor Material

An MO semiconductor material is obtained by doping praseodymium oxide asa charge transportation center into InSnZnO, and doping europium oxideas a carrier control agent to form a praseodymium oxide- and europiumoxide-doped InSnZnO (Pr—Eu:InSnZnO) semiconductor material.

MO is SnZnO, In:Sn:Zn=3:1:1 mol, which is denoted as In(3)Sn(1)Zn(1); inIn_(x)(SnZn)_(y) Eu_(n) Pr_(m)O_(z), x=0.5, y=0.3333, m=0.05, andn=0.1167. However, the present invention is not limited to the foregoingratios. In some embodiments, x=0.53, y=0.353, m=0.05, n=0.067, or,x=0.56, y=0.373, m=0.05, n=0.017, or, x=0.58, y=0.387, m=0.03, n=0.003,which will not be repeated herein.

Example 2: Praseodymium Oxide- and Ytterbium Oxide-Doped InZnTiOSemiconductor Material

An MO semiconductor material is obtained by doping praseodymium oxide asa charge transportation center into InZnTiO, and doping ytterbium oxideas a carrier control agent to form a praseodymium oxide- and ytterbiumoxide-doped InZnTiO (Pr—Yb:InZnTiO) semiconductor material.

MO is ZnTiO, In:Zn:Ti=4:1:0.05 mol, which is denoted as In(4) Zn (1) Ti(0.05); in In_(x)(ZnTi)_(y)Yb_(n)Pr_(m)O_(z), x=0.75, y=0.1969,m=0.0031, and n=0.05. However, the present invention is not limited tothe foregoing ratios. In some embodiments, x=0.7, y=0.1838, m=0.0662,n=0.05, or, x=0.65, y=0.17, m=0.13, n=0.05, which will not be repeatedherein.

Example 3: Terbium Oxide- and Europium Oxide-Doped InGaZnO SemiconductorMaterial

An MO semiconductor material is obtained by doping terbium oxide as acharge transportation center into InGaZnO, and doping europium oxide asa carrier control agent to form a terbium oxide- and europiumoxide-doped InGaZnO (Tb—Eu:InGaZnO) semiconductor material.

MO is GaZnO, In:Ga:Zn:=4:0.5:1 mol, which is denoted as In(4) Ga(0.5)Zn(1); in In_(x)(GaZn)_(y)Eu_(n)Tb_(m)O_(z), x=0.65, y=0.2438,m=0.05, and n=0.0562. However, the present invention is not limited tothe foregoing ratios. In some embodiments, x=0.55, y=0.2053, m=0.05,n=0.1937, or, x=0.58, y=0.2175, m=0.05, n=0.1525, or, x=0.6, y=0.225,m=0.05, n=0.125, which will not be repeated herein.

Example 4: Terbium Oxide- and Ytterbium Oxide-Doped InGaZrOSemiconductor Material

An MO semiconductor material is obtained by doping terbium oxide as acharge transportation center into InGaZrO, and doping ytterbium oxide asa carrier control agent to form a terbium oxide- and ytterbiumoxide-doped InGaZrO (Tb—Yb:InGaZrO) semiconductor material.

MO is GaZrO, In:Ga:Zr=5:1:0.05 mol, which is denoted as In(5) Ga (1) Zr(0.05): in In_(x)(GaZr)_(y) Yb_(n)Tb_(m)O_(z), x=0.7, y=0.147, m=0.103,and n=0.05. However, the present invention is not limited to theforegoing ratios. In some embodiments, x=0.65, y=0.1365, m=0.1635,n=0.05, or, x=0.63, y=1323, m=0.1877, n=0.05, or, x=0.74, y=0.1554,m=0.0546, n:=0.05, which will not be repeated herein.

Example 5: Cerium Oxide- and Europium Oxide-Doped InZnO SemiconductorMaterial

An MO semiconductor material is obtained by doping cerium oxide as acharge transportation center into InZnO, and doping europium oxide as acarrier control agent to form a cerium oxide- and europium oxide-dopedInZnO (Ce—Eu:InZnO) semiconductor material.

MO is ZnO, In:Zn=9:1 mol, which is denoted as In(9) Zn(1); inIn_(x)Zn_(y) Eu_(n) Ce_(m)O_(z), x=0.68, y=0.0756, m=0.1944, and n=0.05.However, the present invention is not limited to the foregoing ratios.In some embodiments, x=0.7, y=0.0778, m=0.1722, n=0.05, or, x=0.75,y=0.0833, m=0.1167, n=0.05, or, x=0.8, y=0.0889, m=0.0611, n=0.05, whichwill not be repeated herein.

Example 6: Dysprosium Oxide- and Ytterbium Oxide-Doped InZnTaOSemiconductor Material

An MO semiconductor material is obtained by doping dysprosium oxide as acharge transportation center into InZnTaO, and doping ytterbium oxide asa carrier control agent to form a dysprosium oxide- and ytterbiumoxide-doped InZnTaO (Dy—Yb:InZnTaO) semiconductor material.

MO is ZnTaO, In:Zn:Ta=3:1:0.1 mol, which is denoted as in(3) Zn (1) Ta(0.1); in In_(x)(ZnTa)_(y)Yb_(n) Dy_(m)O_(z), x=0.58, y=0.2127,m=0.1573, and n=0.05. However, the present invention is not limited tothe foregoing ratios. In some embodiments, x=0.6, y=0.22, m=0.13,n=0.05, or, x=0.65, y=0.2383, m=0.0617, n=0.05, or, x=0.68, y=0.2493,m=0.0207, n=(0.05, which will not be repeated herein.

Example 7: Praseodymium Oxide- and Europium Oxide-Doped InSnZnOThin-Film

An MO semiconductor thin-film is formed through magnetron sputtering ofthe praseodymium oxide- and europium oxide-doped InSnZnO semiconductormaterial of example 1.

Example 8: Praseodymium Oxide- and Ytterbium Oxide-Doped InZnTiOThin-Film

An MO semiconductor thin-film is formed through magnetron sputtering ofthe praseodymium oxide- and ytterbium oxide-doped InZnTiO semiconductormaterial of example 2.

Example 9: Terbium Oxide- and Europium Oxide-Doped InGaZnO Thin-Film

An MO semiconductor thin-film is formed through magnetron sputtering ofthe terbium oxide- and europium oxide-doped InGaZnO semiconductormaterial of example 3.

Example 10: Terbium Oxide- and Ytterbium Oxide-Doped InGaZrO Thin-Film

An MO semiconductor thin-film is formed through magnetron sputtering ofthe terbium oxide- and ytterbium oxide-doped InGaZrO semiconductormaterial of example 4.

Example 11: Cerium Oxide- and Europium Oxide-Doped InZnO Thin-Film

An MO semiconductor thin-film is prepared from the cerium oxide- andeuropium oxide-doped InZnO semiconductor material of example 5 by usinga solution method.

Example 12: Dysprosium Oxide- and Ytterbium Oxide-Doped InZnTaOThin-Film

An MO semiconductor thin-film is formed through magnetron sputtering ofthe dysprosium oxide- and ytterbium oxide-doped InZnTaO semiconductormaterial of example 6.

Example 13: Thin-Film Transistor

A thin-film transistor has a back-channel etch structure, with theschematic structural diagram shown in FIG. 1 . The thin-film transistoris provided with a substrate 01, a gate electrode 05 located on thesubstrate 01, an insulating layer 04 located on the substrate 01 and thegate electrode 05, a channel layer 03 covering the upper surface of theinsulating layer 04 and corresponding to the gate electrode 05, a sourceelectrode 07-1 and a drain electrode 07-2 both spaced apart from eachother and electrically connected with both ends of the channel layer 03,and a spacer layer 06.

The substrate 01 is a hard alkali-free glass substrate, which is coveredwith a buffer layer 02 which is silicon oxide.

The gate electrode 05 has a metal molybdenum/copper (Mo/Cu) laminatedstructure prepared through magnetron sputtering, with a thickness of20/400 nm.

The insulating layer 04 is a laminated structure of silicon nitride(Si₃N₄) and silicon oxide (SiO₂) prepared by chemical vapor deposition,with a thickness of 250/50 nm, where the silicon nitride is in contactwith the gate electrode 05 at the lower layer and the silicon oxide isin contact with the channel layer 03 at the upper layer.

To test the impact of different praseodymium oxide content on deviceperformance, the channel layer 03 is made of the praseodymium oxide- andeuropium oxide-doped InSnZnO semiconductor material of example 1. Threeceramic targets, InSnZnO, europium oxide-doped InSnZnO (Eu:InSnZnO) andpraseodymium oxide- and europium oxide-doped InSnZnO (Pr—Eu:InSnZnO),are used to prepare thin-films with different ingredient ratios throughco-sputtering of a single or two targets and by adjusting the sputteringpower of the two targets.

The source electrode 07-1 and the drain electrode 07-2 have a metalmolybdenum/copper (Mo/Cu) laminated structure with a thickness of 20/400nm. The source electrode 07-1 and the drain electrode 07-2 are patternedwith a commercial hydrogen peroxide-based etchant, which has less damageto the channel layer 03 and no obvious etching residue.

The spacer layer 06 is made of silicon oxide (SiO₂) prepared by chemicalvapor deposition with a thickness of 300 nm and a deposition temperatureof 250° C.

The thin-film transistor of this embodiment may have a closed structureincluding only a substrate 01, a gate electrode 05, an insulating layer04, a channel layer 03, a source electrode 07-1, a drain electrode 07-2,and a spacer layer 06, may further include a planarization layer, areflective electrode, a pixel definite layer, etc., and may further beintegrated with other devices.

The patterning process of the thin-film is implemented byphotolithography combined with wet or dry etching.

In this embodiment, the specific parameters and the performance of theprepared thin-film transistor device are shown in Table 1. Thecharacterization mode of photo-current characteristics is to irradiatethe channel layer 03 of the thin-film transistor device with acommercial white LED light source (the light intensity is set to 10000nits), evaluate the transfer characteristics of the device underillumination and under no illumination, and extract changes of thresholdvoltage and subthreshold swing, etc. of the device to evaluate thestrength of the characteristics. When the variation range of thethreshold voltage is large, it indicates that the photo-currentcharacteristics are strong, and when the variation range of thethreshold voltage is small, the photo-current characteristics are weak.

Test 1 2 3 4 5 6 7 8 Praseodymium atom m 0 0 0.0001 0.0010 0.0100 0.05000.1000 0.1500 content Europium atom n 0 0.0500 0.0500 content DepositionDeposition mode Magnetron sputtering conditions of the O₂/(Ar + O₂) (%)20 channel layer Sputtering 0.5 pressure (Pa) Substrate RT temperature(° C.) Channel layer Atmosphere Air-350° C. treatment annealingtreatment Composition of Substrate Glass other film layers Buffer LayerSiO₂ Gate electrode Mo/Cu Gate insulating Si₃N₄/SiO₂ layer Sourceelectrode Mo/Cu and drain electrode Spacer layer SiO₂ Spacer layerAtmosphere Air-300° C. post-treatment annealing treatment Thin-filmproperties Carrier 5.00E+19 4.20E+18 4.00E+18 3.50E+18 2.80E+18 8.40E+173.10E+17 8.00E+16 concentration n (cm⁻³) Device performance Thresholdvoltage / −5.3 −4.8 −4.2 −1.4 0.2 2.6 4.1 V_(th) (V) Mobility μ / 40.638.4 34.8 30.5 25.7 12.2 3.5 (cm²V⁻¹s⁻¹) Subthreshold / 0.14 0.14 0.160.18 0.25 0.34 0.46 swing SS (V/decade) Current on/off) / 10⁹ 10⁹ 10⁹10⁹ 10⁹ 10⁸ 10⁷ ratio I_(on)/I_(off) Electrical / Poor Relatively GoodExcellent Excellent Excellent Excellent stability poor Photo-current /Extremely Strong Relatively Weak Weak Weak Weak characteristics strongstrong Note: MO in this embodiment is SnZnO, where In/Sn/Zn =3/1/1(mol), and “/” indicates that the device has no on-offcharacteristics.

It can be seen from Table 1 that the doping of praseodymium oxide andeuropium oxide has a very obvious impact on the device performance.First, as shown in Test 1 of Table 1, the device prepared from InSnZnOwithout praseodymium oxide (m=0) and europium oxide (n=0) does not showthe “on-off” characteristics (on-state) of a thin-film transistor, whichindicates that the carrier concentration in the thin-film is too high.As shown in Test 2 of Table 1, after doping of a certain amount ofeuropium oxide (corresponding to m=0, n=0.05), the device shows “on-off”characteristics, with details shown in FIG. 4(a), which indicates thatthe doping of europium oxide can effectively suppress the carrierconcentration in the thin-film, and corresponding Hall data of thethin-film is shown in Table 1. Further, as shown in Tests 2-8 in Table1, a series of devices with different praseodymium content can beprepared by adjusting the sputtering power of targets in co-sputtering.It should be noted that the device not doped with praseodymium oxide(corresponding to m=0, n=0.05) has relatively high mobility, smallsubthreshold swing and negative threshold voltage, but its photo-currentcharacteristics are extremely strong. That is, the devicecharacteristics change obviously under the condition of lightirradiation (the threshold voltage shifts negatively and thesubthreshold swing degrades seriously). However, after the doping of acertain amount of praseodymium oxide, the photo-current characteristicsof the device are obviously inhibited. Certainly, with the increase ofthe praseodymium oxide content, the mobility and other characteristicsof the device are further degraded, and the photo-currentcharacteristics are further improved. After excessive praseodymium oxideis doped (for example, m=0.15, n=0.05), the mobility of the device isobviously degraded. Although the photo-current characteristics of thedevice are extremely weak, this greatly limits its application fields.Therefore, in practical application, it is necessary to weigh therelationship between the two and select the appropriate doping amount.

The corresponding photo-current characteristics of the device preparedin this embodiment are tested. As shown in FIG. 4(b) and FIG. 4(c), thecorresponding m values are 0 and 0.05, respectively. When lightirradiates on the device, the threshold voltage of the device(corresponding to m=0, n=0.05) not doped with praseodymium oxide shiftssignificantly negatively, and the subthreshold swing is seriouslydegraded. Ater a certain amount of praseodymium oxide is doped(corresponding to m=0.05, n=0.05), the threshold voltage of the devicehas almost no change. The device shows excellent illumination stability,which corresponds to the weak photo-current characteristics in Table 1.

The test results of this embodiment show that doping a certain amount ofpraseodymium oxide and europium oxide into the InSnZnO basis materialcan effectively control the carrier concentration of the material andimprove illumination stability.

Example 14: Thin-Film Transistor

A thin-film transistor has a back-channel etch structure, with theschematic structural diagram shown in FIG. 1 . The thin-film transistoris provided with a substrate 01, a gate electrode 05 located on thesubstrate 01, an insulating layer 04 located on the substrate 01 and thegate electrode 05, a channel layer 03 covering the upper surface of theinsulating layer 04 and corresponding to the gate electrode 05, a sourceelectrode 07-1 and a drain electrode 07-2 both spaced apart from eachother and electrically connected with both ends of the channel layer 03,and a spacer layer 06.

The substrate 01 is a hard alkali-free glass substrate, which is coveredwith a buffer layer 02 which is silicon oxide.

The gate electrode 05 has a metal molybdenum/copper (Mo/Cu) laminatedstructure prepared through magnetron sputtering, with a thickness of20/400 nm.

The insulating layer 04 is a laminated structure of silicon nitride(Si₃N₄) and silicon oxide (SiO₂) prepared by chemical vapor deposition,with a thickness of 250/50 nm, where the silicon nitride is in contactwith the gate electrode 05 at the lower layer and the silicon oxide isin contact with the channel layer 03 at the upper layer.

To test the impact of different ytterbium oxide content on deviceperformance, the channel layer 03 is made of the praseodymium oxide- andytterbium oxide-doped InZnTiO semiconductor material of example 2. Threeceramic targets, InZnTiO, praseodymium oxide-doped InSnZnO (Pr:InZnTiO)and praseodymium oxide- and ytterbium oxide-doped InZnTiO(Pr—Yb:InZnTiO), are used to prepare thin-films with differentingredient ratios through co-sputtering of a single or two targets andby adjusting the sputtering power of the two targets.

The source electrode 07-1 and the drain electrode 07-2 have a metalmolybdenum/copper (Mo/Cu) laminated structure with a thickness of 20/400nm. The source electrode 07-1 and the drain electrode 07-2 are patternedwith a commercial hydrogen peroxide-based etchant, which has less damageto the channel layer 03 and no obvious etching residue.

The spacer layer 06 is made of silicon oxide (SiO₂) prepared by chemicalvapor deposition with a thickness of 300 nm and a deposition temperatureof 250° C.

The thin-film transistor of this embodiment may have a closed structureincluding only a substrate 01, a gate electrode 05, an insulating layer04, a channel layer 03, a source electrode 07-1, a drain electrode 07-2,and a spacer layer 06, may further include a planarization layer, areflective electrode, a pixel definite layer, etc., and may further beintegrated with other devices.

The patterning process of the thin-film is implemented byphotolithography combined with wet or dry etching.

In this embodiment, the specific parameters and the performance of theprepared thin-film transistor device are shown in Table 2. Thecharacterization mode of photo-current characteristics is to irradiatethe channel layer 03 of the thin-film transistor device with acommercial white LED light source (the light intensity is set to 1000nits), evaluate the transfer characteristics of the device underillumination and under no illumination, and extract changes of thresholdvoltage and subthreshold swing, etc. of the device to evaluate thestrength of the characteristics. When the variation range of thethreshold voltage is large, it indicates that the photo-currentcharacteristics are strong, and when the variation range of thethreshold voltage is small, the photo-current characteristics are weak.

Test 1 2 3 4 5 6 7 8 Praseodymium m 0 0.0500 0.0500 atom contentYtterbium atom n 0 0 0.0001 0.0010 0.0100 0.0500 0.1000 0.1500 contentDeposition Deposition Magnetron sputtering conditions of the modechannel layer O₂/(Ar + O₂) (%) 30 Sputtering 0.3 pressure (Pa) SubstrateRT temperature (° C.) Channel layer Atmosphere Air-350° C. treatmentannealing treatment Composition of Substrate Glass other film layersBuffer layer SiO₂ Gate electrode Mo/Cu Gate insulating Si₃N₄/SiO₂ layerSource electrode Mo/Cu and drain electrode Spacer layer SiO₂ Spacerlayer Atmosphere Air-300° C. post-treatment annealing treatmentThin-film Carrier 3.30E+19 2.10E+19 9.30E+18 7.50E+18 5.20E+18 8.50E+172.40E+17 6.60E+17 properties concentration n (cm⁻³) Device Threshold / /−15.8 −6.2 −1.2 0.5 2.8 5.2 performance voltage V_(th) (V) Mobility μ // 56.3 48.6 36.2 30.7 15.2 6.5 (cm²V⁻¹s⁻¹) Subthreshold / / 0.34 0.140.19 0.23 0.36 0.53 swing SS (V/decade) Current on/off / / 10⁸ 10⁹ 10⁹10⁹ l0⁸ 10⁷ ratio I_(on)/I_(off) Electrical / / Relatively PoorExcellent Excellent Excellent Excellent stability poor Photo-current / /Weak Weak Weak Weak Weak Weak Characteristics Note: MO in thisembodiment is ZnTiO, where In/Zn/Ti = 4/1/0.05 (mol), and “/” indicatesthat the device has no on-off characteristics.

It can be seen from Table 2 that the doping of praseodymium oxide andytterbium oxide has a very obvious impact on the device performance.First, as shown in Test 1 of Table 2, the device prepared from InZnTiOwithout praseodymium oxide (m=0) and ytterbium oxide (n=0) does not showthe “on-off” characteristics (on-state) of a thin-film transistor, whichindicates that the carrier concentration in the thin-film is too high.As shown in Test 2 of Table 2, after doping of a certain amount(corresponding to m=0.05, n=) of praseodymium oxide, the device stilldoes not show “on-off” characteristics; further, when a certain amountof ytterbium oxide continues to be doped (corresponding to m=0.05,n=0.0001), the device shows “on-off” characteristics. It indicates thatthe suppression effect of praseodymium oxide on the carrierconcentration in thin-films is not as obvious as that of ytterbiumoxide, and corresponding Hall data of the thin-films is shown in Table2. To further study the impact of ytterbium oxide, as shown in Tests 2-8in Table 2, a series of devices with different ytterbium content can beprepared by adjusting the sputtering power of targets in co-sputtering.Specifically, devices doped with a small amount of ytterbium oxide(corresponding to m=0.05, n=0.0001) have relatively high mobility andnegative threshold voltage. With the increase of ytterbium oxidecontent, the threshold voltage of the device shifts positively and themobility decreases. It shows that ytterbium oxide can effectivelycontrol the threshold voltage of the devices, that is, ytterbium oxideeffectively controls the carrier concentration in thin-films, which canbe further verified from Hall data in Table 2. Certainly, afterexcessive ytterbium oxide is doped (for example, m=0.05, n=0.15), themobility of the device is obviously degraded. This greatly limits itsapplication fields. Therefore, in practical application, it is necessaryto weigh the relationship between the two and select the appropriatedoping amount.

The corresponding photo-current characteristics of the device preparedin this embodiment are tested. As shown in FIG. 5(b) and FIG. 5(c), thecorresponding m values are 0.05, and n values are 0.001 and 0.05respectively. When light irradiates on the device, the threshold voltageof the device (corresponding to m=0.05, n=0.001) doped with a smallamount of ytterbium oxide does not shift significantly, and thesubthreshold swing is slightly degraded. In addition, after a certainamount of ytterbium oxide is doped (corresponding to m=0.05, n=0.05),the threshold voltage of the device also has almost no change. Thedevice shows excellent illumination stability, which corresponds to theweak photo-current characteristics in Table 2. It should be noted thatthe photo-current characteristics of devices with different ytterbiumcontent (m=0.05, n=0-0.15) are weak, which indicates that the doping ofpraseodymium oxide can effectively improve the illumination stability ofthe devices.

The test results of this embodiment show that doping a certain amount ofpraseodymium oxide and ytterbium oxide into the InZnTiO basis materialcan effectively control the carrier concentration of the material andimprove illumination stability.

Example 15: Thin-Film Transistor

A thin-film transistor has a top-gate self-alignment structure, with theschematic structural diagram shown in FIG. 2 . The thin-film transistoris provided with a substrate 01, a buffer layer 02, a channel layer 03,an insulating layer 04 and a gate electrode 05 both located on thechannel layer 03, a spacer layer 06 covering the channel layer 03 andthe upper surface of the gate electrode, and a source electrode 07-1 anda drain electrode 07-2 both located on the spacer layer 06 andelectrically connected with both ends of the channel layer 03.

The substrate 01 is a hard glass substrate.

The buffer layer 02 is silicon oxide prepared by plasma-enhancedchemical vapor deposition.

The channel layer 03 is made of the terbium oxide- and europiumoxide-doped InGaZnO semiconductor material of example 3, with athickness of 30 nm.

The insulating layer 04 is silicon oxide with a thickness of 300 nm. Thegate electrode 05 has a titanium/copper (Ti/Cu) laminated structureprepared through magnetron sputtering, with a thickness of 20/400 nm.

The spacer layer 06 is silicon oxide with a thickness of 300 nm.

The source electrode 07-1 and the drain electrode 07-2 each have atitanium/copper (Ti/Cu) laminated structure prepared through magnetronsputtering, with a thickness of 20/400 nm.

To test the impact of different ytterbium content on device performance,the channel layer 03 is made of the terbium oxide- and europiumoxide-doped InGaZnO semiconductor material of example 3. Three ceramictargets, InGaZnO, terbium oxide-doped InGaZnO (Tb:InGaZnO) and terbiumoxide- and europium oxide-doped InGaZnO (Tb—Eu:InGaZnO), are used toprepare thin-films with different ingredient ratios throughco-sputtering of a single or two targets and by adjusting the sputteringpower of the two targets.

The thin-film transistor of this embodiment may have a closed structureincluding only a substrate 01, a channel layer 03, an insulating layer04, a gate electrode 05, a spacer layer 06, a source electrode 07-1 anda drain electrode 07-2, may further include a passivation layer, a pixeldefinite layer, etc., and may further be integrated with other devices.

The patterning of the thin-film is implemented by photolithographycombined with wet or dry etching.

In this embodiment, the specific parameters and the performance of theprepared thin-film transistor device are shown in Table 3. Thecharacterization mode of photo-current characteristics is to irradiatethe channel layer of the thin-film transistor device with a commercialwhite LED light source, characterize the transfer characteristics of thedevice under different light intensity conditions, and extract changesof threshold voltage of the device to evaluate the strength of thecharacteristics. When the variation range of the threshold voltage islarge, it indicates that the photo-current characteristics are strong,and when the variation range of the threshold voltage is small, thephoto-current characteristics are weak.

Test 1 2 3 4 5 6 7 8 Terbium atom m 0 0.0500 0.0500 content Europiumatom n 0 0 0.0001 0.0010 0.0100 0.0500 0.1000 0.1500 content DepositionDeposition Magnetron sputtering conditions of the mode channel layerO₂/(Ar + O₂) (%) 20 Sputtering pressure 0.3 (Pa) Substrate RTtemperature (° C.) Channel layer Atmosphere Air-350° C. treatmentannealing treatment Composition of Substrate Glass other film layersBuffer layer Si₃N₄/SiO₂ Gate insulating SiO2 layer Gate electrode Ti/CuSpacer layer SiO₂ Source electrode Ti/Cu and drain electrode Spacerlayer Atmosphere Air-300° C. post-treatment annealing treatmentThin-film Carrier 2.60E+19 1.00E+19 9.10E+18 5.00E+18 1.20E+18 5.40E+178.30E+16 2.02E+16 properties concentration n (cm⁻³) Device Threshold / /−14.8 −5.2 −0.6 −0.8 3.6 6.4 performance voltage V_(th) (V) Mobility μ // 56.3 36.8 26.3 20.2 8.2 1.5 (cm²V⁻¹s⁻¹) Subthreshold / / 0.43 0.220.29 0.33 0.38 0.55 swing SS (V/decade) Current on/off / / 10⁸ 10⁹ 10⁹10⁹ l0⁸ 10⁷ ratio I_(on)/I_(off) Electrical / / Relatively PoorExcellent Excellent Excellent Excellent stability poor Photo-current / /Weak Weak Weak Weak Weak Weak Characteristics Note: MO in thisembodiment is GaZnO, where In/GA/Zn = 4/0.5/1 (mol), and “/” indicatesthat the device has no on-off characteristics.

It can be seen from Table 3 that the doping of terbium oxide andeuropium oxide has a very obvious impact on the device performance.First, as shown in Test 1 of Table 3, the device prepared from InGaZnOwithout terbium oxide (m=0) and europium oxide (n=0) does not show the“on-off” characteristics (on-state) of a thin-film transistor, whichindicates that the carrier concentration in the thin-film is too high.As shown in Test 2 of Table 3, after doping of a certain amount(corresponding to m=0.05, n=0) of terbium oxide, the device still doesnot show “on-off” characteristics; further, when a certain amount ofeuropium oxide continues to be doped (corresponding to m=0.05,n=0.0001), the device shows “on-off” characteristics. It indicates thatthe suppression effect of terbium oxide on the carrier concentration inthin-films is not as obvious as that of europium oxide, andcorresponding Hall data of the thin-films are shown in Table 3. Tofurther study the impact of europium oxide, as shown in Tests 2-8 inTable 3, a series of devices with different europium content can beprepared by adjusting the sputtering power of targets in co-sputtering.Specifically, devices doped with as mall amount of europium oxide(corresponding to m=0.05, n-=0.001) have relatively high mobility andnegative threshold voltage. With the increase of europium oxide content,the threshold voltage of the device shifts positively and the mobilitydecreases. It shows that europium oxide can effectively control thethreshold voltage of the devices, that is, europium oxide effectivelycontrols the carrier concentration in thin-films, which can be furtherverified from Hall data in Table 3. Certainly, after excessive europiumoxide is doped (for example, m=0.05, n=0.15), the mobility of the deviceis obviously degraded. This greatly limits its application fields.Therefore, in practical application, it is necessary to weigh therelationship between the two and select the appropriate doping amount.The corresponding photo-current characteristics of the device preparedin this embodiment are tested. As shown in FIG. 6(b) and FIG. 6(c), thecorresponding m values are 0.05, and n values are 0.001 and 0.05respectively. When light irradiates on the device, the threshold voltageof the device (corresponding to m=0.05, n=0.001) doped with a smallamount of europium oxide does not shift significantly, and thesubthreshold swing is slightly degraded. In addition, after a certainamount of europium oxide is doped (corresponding to m=0.05, n=0.05), thethreshold voltage of the device also has almost no change. The deviceshows excellent illumination stability, which corresponds to the weakphoto-current characteristics in Table 3. It should be noted that thephoto-current characteristics of devices with different europium content(m=0.05, n=0-0.15) are weak, which indicates that the doping of terbiumoxide can effectively improve the illumination stability of the devices.

The test results of this embodiment show that doping a certain amount ofterbium oxide and europium oxide into the InGaZnO basis material caneffectively control the carrier concentration of the material andimprove illumination stability.

Example 16: Thin-Film Transistor

A thin-film transistor has a top-gate self-alignment structure, with theschematic structural diagram shown in FIG. 2 . The thin-film transistoris provided with a substrate 01, a buffer layer 02, a channel layer 03,an insulating layer 04 and a gate electrode 05 both located on thechannel layer 03, a spacer layer 06 covering the channel layer 03 andthe upper surface of the gate electrode, and a source electrode 07-1 anda drain electrode 07-2 both located on the spacer layer 06 andelectrically connected with both ends of the channel layer 03.

The substrate 01 is a hard glass substrate.

The buffer layer 02 is silicon oxide prepared by plasma-enhancedchemical vapor deposition.

The channel layer 03 is made of the terbium oxide- and ytterbiumoxide-doped InGaZrO semiconductor material of example 4, with athickness of 30 nm.

The insulating layer 04 is silicon oxide with a thickness of 300 nm. Thegate electrode 05 has a titanium/copper (Ti/Cu) laminated structureprepared through magnetron sputtering, with a thickness of 20/400 nm.

The spacer layer 06 is silicon oxide with a thickness of 300 nm.

The source electrode 07-1 and the drain electrode 07-2 each have atitanium/copper (Ti/Cu) laminated structure prepared through magnetronsputtering, with a thickness of 20/400 nm.

To test the impact of different terbium content on device performance,the channel layer 03 is made of the terbium oxide- and ytterbiumoxide-doped InGaZrO semiconductor material of example 4. Three ceramictargets, InGaZrO, terbium oxide-doped InGaZnO (Tb:InGaZrO) and terbiumoxide- and ytterbium oxide-doped InGaZnO (Tb—Yb:InGaZrO), are used toprepare thin-films with different ingredient ratios throughco-sputtering of a single or two targets and by adjusting the sputteringpower of the two targets.

The thin-film transistor of this embodiment may have a closed structureincluding only a substrate 01, a channel layer 03, an insulating layer04, a gate electrode 05, a spacer layer 06, a source electrode 07-1 anda drain electrode 07-2, may further include a passivation layer, a pixeldefinite layer. etc., and may further be integrated with other devices.

The patterning of the thin-film is implemented by photolithographycombined with wet or dry etching.

In this embodiment, the specific parameters and the performance of theprepared thin-film transistor device are shown in Table 4. Thecharacterization mode of photo-current characteristics is to irradiatethe channel layer 03 of the thin-film transistor device with acommercial white LED light source, characterize the transfercharacteristics of the device under different light intensityconditions, and extract changes of threshold voltage of the device toevaluate the strength of the characteristics. When the variation rangeof the threshold voltage is large, it indicates that the photo-currentcharacteristics are strong, and when the variation range of thethreshold voltage is small, the photo-current characteristics are weak.

Test 1 2 3 4 5 6 7 8 Terbium atom m 0 0 0.0001 0.0010 0.0100 0.05000.1000 0.1500 content Ytterbium atom n 0 0.0500 0.0500 contentDeposition Deposition mode Magnetron sputtering conditions of theO₂/(Ar + O₂) (%) 30 channel layer Sputtering pressure 0.5 (Pa) SubstrateRT temperature (° C.) Channel layer Atmosphere Air-350° C. treatmentannealing treatment Composition of Substrate Glass other film layersBuffer layer Si₃N₄/SiO₂ Gate insulating SiO2 layer Gate electrode Ti/CuSpacer layer SiO₂ Source electrode Ti/Cu and drain electrode Spacerlayer Atmosphere Air-300° C. post-treatment annealing treatmentThin-film Carrier 8.00E+19 7.20E+18 7.00E+18 6.50E+18 4.80E+18 1.20E+185.10E+17 8.50E+16 properties concentration n (cm⁻³) Device Threshold /−6.3 −5.8 −5.2 −2.4 0.1 1.6 3.1 performance voltage V_(th) (V) Mobilityμ / 45.6 40.5 38.8 32.5 28.7 14.2 6.5 (cm²V⁻¹s⁻¹) Subthreshold / 0.120.12 0.13 0.15 0.24 0.32 0.45 swing SS (V/decade) Current on/off ratio /10⁹ 10⁹ 10⁹ 10⁹ 10⁹ l0⁸ 10⁷ ratio I_(on)/I_(off) Electrical / PoorRelatively Good Excellent Excellent Excellent Excellent stability poorPhoto-current / Extremely Strong Relatively Weak Weak Weak WeakCharacteristics strong strong Note: MO in this embodiment is GaZrO,where In/Ga/Zr = 5/1/0.05 (mol), and “/” indicates that the device hasno on-off characteristics.

It can be seen from Table 4 that the doping of terbium oxide andytterbium oxide has a very obvious impact on the device performance.First, as shown in Test 1 of Table 4, the device prepared from InGaZrOwithout terbium oxide (m=0) and ytterbium oxide (n=0) does not show the“on-off” characteristics (on-state) of a thin-film transistor, whichindicates that the carrier concentration in the thin-film is too high.As shown in Test 2 of Table 4, after doping of a certain amount ofytterbium oxide (corresponding to m=0, n=0.05), the device shows“on-off” characteristics, with details shown in FIG. 7(a), whichindicates that the doping of ytterbium oxide can effectively suppressthe carrier concentration in the thin-film, and corresponding Hall dataof the thin-film is shown in Table 4. Further, as shown in Tests 2-8 inTable 4, a series of devices with different terbium content can beprepared by adjusting the sputtering power of targets in co-sputtering.It should be noted that the device not doped with terbium oxide(corresponding to m=0, n=0.05) has relatively high mobility, smallsubthreshold swing and negative threshold voltage, but its photo-currentcharacteristics are extremely strong. That is, the devicecharacteristics change obviously under the condition of lightirradiation (the threshold voltage shifts negatively and thesubthreshold swing degrades seriously). However, after the doping of acertain amount of terbium oxide, the photo-current characteristics ofthe device are obviously inhibited. Certainly, with the increase of theterbium oxide content, the mobility and other characteristics of thedevice are further degraded, and the photo-current characteristics arefurther improved. After excessive terbium oxide is doped (for example,m=0.15, n=0.05), the mobility of the device is obviously degraded.Although the photo-current characteristics of the device are extremelyweak, this greatly limits its application fields. Therefore, inpractical application, it is necessary to weigh the relationship betweenthe two and select the appropriate doping amount.

The corresponding photo-current characteristics of the device preparedin this embodiment are tested. As shown in FIG. 7(b) and FIG. 7(c), thecorresponding n values are 0.05, and m values are 0 and 0.05respectively. When light irradiates on the device, the threshold voltageof the device (corresponding to m=0, n=0.05) without terbium oxideshifts negatively significantly, and the subthreshold swing is seriouslydegraded. In addition, after a certain amount of terbium oxide is doped(corresponding to m=0.05, n=0.05), the threshold voltage of the devicehas almost no change. The device shows excellent illumination stability,which corresponds to the weak photo-current characteristics in Table 4.

The test results of this embodiment show that doping a certain amount ofterbium oxide and ytterbium oxide into the InGaZrO basis material caneffectively control the carrier concentration of the material andimprove illumination stability.

Example 17: Thin-Film Transistor

A thin-film transistor has a self-alignment structure, with theschematic structural diagram shown in FIG. 2 . The thin-film transistoris provided with a substrate 01, a buffer layer 02, a channel layer 03,an insulating layer 04 and a gate electrode 05 both located on thechannel layer 03, a spacer layer 06 covering the channel layer 03 andthe upper surface of the gate electrode 05, and a source electrode 07-1and a drain electrode 07-2 both located on the spacer layer 06 andelectrically connected with both ends of the channel layer 03.

The substrate 01 is a hard glass substrate.

The buffer layer 02 is silicon oxide prepared by plasma-enhancedchemical vapor deposition.

The channel layer 03 is made of the cerium oxide- and europiumoxide-doped InZnO semiconductor material of example 5, with a thicknessof 20 nm.

The insulating layer 04 is silicon oxide with a thickness of 300 nm. Thegate electrode 05 has a molybdenum/copper/molybdenum (Mo/Cu/Mo)laminated structure prepared through magnetron sputtering, with athickness of 20/400/50 nm.

The spacer layer 06 is a silicon oxide thin-film prepared byplasma-enhanced chemical vapor deposition, with a thickness of 300 nm.

The source electrode 07-1 and the drain electrode 07-2 each have amolybdenum/copper/molybdenum (Mo/Cu/Mo) laminated structure preparedthrough magnetron sputtering, with a thickness of 20/400/50 nm.

The thin-film transistor of this embodiment may have a closed structureincluding only a substrate 01, a channel layer 03, an insulating layer04, a gate electrode 05, a spacer layer 06, a source electrode 07-1 anda drain electrode 07-2, may further include a passivation layer, a pixeldefinite layer, etc., and may further be integrated with other devices.

The patterning of the thin-film is implemented by photolithographycombined with wet or dry etching.

In this embodiment, the specific parameters and the performance of theprepared thin-film transistor device are shown in Table 5. Thecharacterization mode of photo-current characteristics is to irradiatethe channel layer 03 of the thin-film transistor device with acommercial white LED light source, characterize the transfercharacteristics of the device under different light intensityconditions, and extract changes of threshold voltage of the device toevaluate the strength of the characteristics. When the variation rangeof the threshold voltage is large, it indicates that the photo-currentcharacteristics are strong, and when the variation range of thethreshold voltage is small, the photo-current characteristics are weak.

Test 1 2 3 4 5 6 7 8 Cerium atom m 0 0 0.0001 0.0010 0.0100 0.05000.1000 0.1500 content Europium atom n 0 0.0500 0.0500 content DepositionDeposition mode Solution method conditions of the Prebaking 120 channellayer temperature (° C.) Channel layer Post-annealingure 400 treatmenttemperature (° C.) Composition of Substrate Glass other film layersBuffer layer SiO₂ Gate insulating SiO2 layer Gate electrode Mo/Cu/MoSpacer layer SiO₂ Source electrode Mo/Cu/Mo and drain electrode Spacerlayer Atmosphere CDA-300° C. post-treatment annealing treatmentThin-film Carrier 5.00E+19 4.20E+18 4.00E+18 3.50E+18 2.80E+18 8.00E+173.10E+17 8.40E+16 properties concentration n (cm⁻³) Device Threshold /−4.2 −4.1 −3.5 −2.3 0.5 2.0 3.2 performance voltage V_(th) (V) Mobilityμ / 52.3 50.6 48.23 35.4 28.1 19.7 8.3 (cm²V⁻¹s⁻¹) Subthreshold / 0.110.11 0.12 0.13 0.29 0.34 0.48 swing SS (V/decade) Current on/off / 10⁹10⁹ 10⁹ 10⁹ 10⁹ l0⁸ 10⁸ ratio I_(on)/I_(off) Electrical / PoorRelatively Good Excellent Excellent Excellent Excellent stability poorPhoto-current / Extremely Strong Relatively Weak Weak Weak Weakcharacteristics strong strong Note: MO in this embodiment is ZnO, whereIn/Zn = 9/1, and “/” indicates that the device has no on-offcharacteristics.

It can be seen from Table 5 that the doping of cerium oxide and europiumoxide has a very obvious impact on the device performance. First, asshown in Test 1 of Table 5, the device prepared from InZnO withoutcerium oxide (m=0) and europium oxide (n=0) does not show the “on-off”characteristics (on-state) of a thin-film transistor, which indicatesthat the carrier concentration in the thin-film is too high. As shown inTest 2 of Table 5, after doping of a certain amount of europium oxide(corresponding to m=0, n=0.05), the device shows “on-off”characteristics, with details shown in FIG. 8(a), which indicates thatthe doping of europium oxide can effectively suppress the carrierconcentration in the thin-film, and corresponding Hall data of thethin-film is shown in Table 5. Further, as shown in Tests 2-8 in Table5, a series of devices with different cerium content can be prepared byadjusting the components in the prepared solution. It should be notedthat the device not doped with cerium oxide (corresponding to m=0,n=0.05) has relatively high mobility, small subthreshold swing andnegative threshold voltage, but its photo-current characteristics areextremely strong. That is, the device characteristics change obviouslyunder the condition of light irradiation (the threshold voltage shiftsnegatively and the subthreshold swing degrades seriously). However,after the doping of a certain amount of cerium oxide, the photo-currentcharacteristics of the device are obviously inhibited. Certainly, withthe increase of the cerium oxide content, the mobility and othercharacteristics of the device are further degraded, and thephoto-current characteristics are further improved. After excessivecerium oxide is doped (for example, m=0.15, n=0.05), the mobility of thedevice is obviously degraded. Although the photo-current characteristicsof the device are extremely weak, this greatly limits its applicationfields. Therefore, in practical application, it is necessary to weighthe relationship between the two and select the appropriate dopingamount.

The corresponding photo-current characteristics of the device preparedin this embodiment are tested. As shown in FIG. 8(b) and FIG. 8(c), thecorresponding n values are 0.05, and m values are 0 and 0.05respectively. When light irradiates on the device, the threshold voltageof the device (corresponding to m=0, n=0.05) without cerium oxide shiftsnegatively significantly, and the subthreshold swing is seriouslydegraded. In addition, after a certain amount of cerium oxide is doped(corresponding to m=0.05, n=0.05), the threshold voltage of the devicehas almost no change. The device shows excellent illumination stability,which corresponds to the weak photo-current characteristics in Table 5.

The test results of this embodiment show that doping a certain amount ofcerium oxide and europium oxide into the InZnO basis material caneffectively control the carrier concentration of the material andimprove illumination stability.

Example 18: Thin-Film Transistor

A thin-film transistor has an etch-stop structure, with the schematicstructural diagram shown in FIG. 3 . The thin-film transistor isprovided with a substrate 01, a gate electrode 05 located on thesubstrate 01, an insulating layer 04 located on the substrate 01 and thegate electrode 05, a channel layer 03 covering the upper surface of theinsulating layer 04 and corresponding to the gate electrode 05, anetch-stop layer 08, a source electrode 07-1 and a drain electrode 07-2both spaced apart from each other and electrically connected with bothends of the channel layer 03, and a spacer layer 06.

The substrate 01 is a glass substrate, which is covered with bufferlayer 02 silicon oxide.

The gate electrode 05 each have a metal Mo/Al/Mo laminated structureprepared through magnetron sputtering, with a thickness of 50/300/50 nm.

The insulating layer 04 is a laminated structure of silicon nitride(Si₃N₄) and silicon oxide (SiO₂) prepared by chemical vapor deposition,with a thickness of 250/50 nm, where the silicon nitride is in contactwith the gate electrode 05 at the lower layer and the silicon oxide isin contact with the channel layer 03 at the upper layer.

To test the impact of different dysprosium oxide content on deviceperformance, the channel layer 03 is made of the dysprosium oxide- andytterbium oxide-doped InZnTaO semiconductor material of example 6. Threeceramic targets, InZnTaO, ytterbium oxide-doped InZnTaO (Yb:InZnTaO) anddysprosium oxide- and ytterbium oxide-doped InZnTiO (Dy—Yb:InZnTaO), areused to prepare thin-films with different ingredient ratios throughco-sputtering of a single or two targets and by adjusting the sputteringpower of the two targets.

The etch-stop layer 08 and the spacer layer 06 are each made of asilicon oxide (SiO₂) thin-film prepared by chemical vapor depositionwith a thickness of 300 nm and a deposition temperature of 300° C.

The source electrode 07-1 and the drain electrode 07-2 each have a metalMo/Al/Mo laminated structure, with a thickness of 50300/50 nm.

In addition, the thin-film transistor of this embodiment may have aclosed structure including only a substrate 01, a gate electrode 05, aninsulating layer 04, a channel layer 03, an etch-stop layer 08, a sourceelectrode 07-1, a drain electrode 07-2, and a passivation layer, mayfurther include a planarization layer, a reflective electrode, a pixeldefinite layer, etc., and may further be integrated with other devices.

The patterning process of the thin-film is implemented byphotolithography combined with wet or dry etching.

In this embodiment, the specific parameters and the performance of theprepared thin-film transistor device are shown in Table 6. Thecharacterization mode of photo-current characteristics is to irradiatethe channel layer 03 of the thin-film transistor device with acommercial white LED light source, evaluate the transfer characteristicsof devices under illumination and no-illumination conditions, andextract changes of threshold voltage of the device to evaluate thestrength of the characteristics. When the variation range of thethreshold voltage is large, it indicates that the photo-currentcharacteristics are strong, and when the variation range of thethreshold voltage is small, the photo-current characteristics are weak.

Test 1 2 3 4 5 6 7 8 Dysprosium atom m 0 0 0.0001 0.0010 0.0100 0.05000.1000 0.1500 content Yitterbium atom n 0 0.0500 0.0500 contentDeposition Deposition mode Magnetron sputtering conditions of theO₂/(Ar + O₂) (%) 10 channel layer Sputtering pressure (Pa) 0.3 Substrate200 temperature (° C.) Channel layer Atmosphere O₂-350° C. treatmentannealing treatment Composition of Substrate Glass other film layersBuffer layer SiO₂ Gate electrode Mo/Al/Mo Gate insulating layerSiO₂/Si₃N₄ Etch-stop layer SiO₂ Source electrode Mo/Al/Mo and drainelectrode Spacer layer SiO₂ Etch-stop Atmosphere O₂-350° C. layerannealing post-treatment treatment Thin-film Carrier 2.20E+19 1.20E+189.50E+17 9.10E+17 8.40E+17 3.00E+17 8.20E+16 3.30E+16 propertiesconcentration n (cm⁻³) Device Threshold / −2.6 −2.5 −2.0 −0.8 0.6 2.46.7 performance voltage V_(th) (V) Mobility μ / 28.3 26.5 25.1 20.8 15.27.6 1.8 (cm²V⁻¹s⁻¹) Subthreshold / 0.21 0.21 0.22 0.24 0.28 0.32 0.46swing SS (V/decade) Current on/off / 10⁹ 10⁹ 10⁹ 10⁹ 10⁹ l0⁸ 10⁷ ratioI_(on)/I_(off) Stability / Poor Relatively Good Excellent ExcellentExcellent Excellent poor Photo-current / Extremely Strong RelativelyWeak Weak Weak Weak characteristics strong strong Note: MO in thisembodiment is ZnTaO, where In/Zn/Ta = 3/1/0.1 mol, and “/” indicatesthat the device has no on-off characteristics.

It can be seen from Table 6 that the doping of dysprosium oxide andytterbium oxide has a very obvious impact on the device performance.First, as shown in Test 1 of Table 6, the device prepared from InZnTaOwithout dysprosium oxide (m=) and ytterbium oxide (n=0) does not showthe “on-off” characteristics (on-state) of a thin-film transistor, whichindicates that the carrier concentration in the thin-film is too high.As shown in Test 2 of Table 6, after doping of a certain amount ofytterbium oxide (corresponding to m=0, n=0.05), the device shows“on-off” characteristics, with details shown in FIG. 9(a), whichindicates that the doping of ytterbium oxide can effectively suppressthe carrier concentration in the thin-film, and corresponding Hall dataof the thin-film is shown in Table 6. Further, as shown in Tests 2-8 inTable 6, a series of devices with different dysprosium content can beprepared by adjusting the sputtering power of corresponding targets. Itshould be noted that the device not doped with dysprosium oxide(corresponding to m=0, n=0.05) has relatively high mobility, smallsubthreshold swing and negative threshold voltage, but its photo-currentcharacteristics are extremely strong. That is, the devicecharacteristics change obviously under the condition of lightirradiation (the threshold voltage shifts negatively and thesubthreshold swing degrades seriously). However, after the doping of acertain amount of dysprosium oxide, the photo-current characteristics ofthe device are obviously inhibited. Certainly, with the increase of thedysprosium oxide content, the mobility and other characteristics of thedevice are further degraded, and the photo-current characteristics arefurther improved. After excessive dysprosium oxide is doped (forexample, m=0.15, n=0.05), the mobility of the device is obviouslydegraded. Although the photo-current characteristics of the device areextremely weak, this greatly limits its application fields. Therefore,in practical application, it is necessary to weigh the relationshipbetween the two and select the appropriate doping amount.

The corresponding photo-current characteristics of the device preparedin this embodiment are tested. As shown in FIG. 9(b) and FIG. 9(c), thecorresponding n values are 0.05, and m values are 0 and 0.05respectively. When light irradiates on the device, the threshold voltageof the device (corresponding to m=0, n=0.05) without dysprosium oxideshifts negatively significantly, and the subthreshold swing is seriouslydegraded. In addition, after a certain amount of dysprosium oxide isdoped (corresponding to m=0.05, n=0.05), the threshold voltage of thedevice has almost no change. The device shows excellent illuminationstability, which corresponds to the weak photo-current characteristicsin Table 6.

The test results of this embodiment show that doping a certain amount ofdysprosium oxide and ytterbium oxide into the InZnTaO basis material caneffectively control the carrier concentration of the material andimprove illumination stability.

Example 19: Display Panel

A display panel includes the thin-film transistor in each of examples13-18, and the thin-film transistor is configured to drive a displayunit in the display panel.

Example 20: Detector

A detector includes the thin-film transistor in each of examples 13-18,and the thin-film transistor is configured to drive a detection unit ofthe detector.

Each functional layer of the thin-film transistor implemented by thepresent invention is further described below.

The substrate in the present invention is not particularly limited, anda substrate 01 well known in the art can be used. For example, thesubstrate is made of hard alkali glass, alkali-free glass, quartz glass,or silicon; or may be made of flexible polyimide (PI), polyethylenenaphthalate (PEN), polyethylene terephthalate (PET), polyethylene (PE),polypropylene (PP), polystyrene (PS), polyether sulfone (PES) or a metalsheet.

The materials of the gate electrode 05 in the present invention are notparticularly limited, and may be arbitrarily selected from materialswell known in the art. For example, the materials are transparentconductive oxides (ITO, AZO, GZO, IZO, ITZO, FTO, etc.), metals (Mo, Al,Cu, Ag, Ti, Au, Ta, Cr, Ni, etc.) and alloys thereof, metals and oxides(ITO/Ag/ITO, IZO/Ag/IZO, etc.), and composite conductive thin-filmsformed by stacking metals (Mo/Al/Mo, Ti/Al/Ti, etc.).

The methods for preparing gate electrode 05 thin-films may besputtering, electroplating, thermal evaporation and other depositionmethods, and preferably sputtering deposition. Because the thin-filmsprepared by this method have good adhesion to a substrate 01 andexcellent uniformity, the thin-films can be prepared in a large area.

Here, the specific structure of the gate electrode needs to bedetermined according to the technical parameters to be achieved. Forexample, if a transparent electrode needs to be used in transparentdisplay, single-layer ITO may be used as the gate electrode orITO/Ag/ITO may be used as the gate electrode. In addition, if a hightemperature process is needed in the application in special fields, ametal alloy thin-film which can resist high temperature may be selectedas the gate electrode.

The materials of the insulating layer 04 in the present invention arenot particularly limited, and may be arbitrarily selected from materialswell known in the art. For example, the materials are silicon oxide,silicon nitride, alumina, tantalum oxide, hafnium oxide, yttrium oxide,and polymer organic film layers.

It should be pointed out that the components of these insulatingthin-films may be inconsistent with a theoretical stoichiometric ratio.In addition, the insulating layer 04 may be formed by stacking variousinsulating films, which can implement better insulating characteristicsand improve the interface characteristics between the channel layer 03and the insulating layer 04. Moreover, the insulating layer 04 may beprepared in various ways, such as physical vapor deposition, chemicalvapor deposition, atomic layer deposition, laser deposition, anodicoxidation or a solution method.

The etchant used in wet etching includes a mixed solution of phosphoricacid, nitric acid and glacial acetic acid or a mixed solution based onhydrogen peroxide. The etching rate of an MO semiconductor material in ahydrogen peroxide-based etchant is less than 1 nm/min. Dry etching, forexample, may be implemented by plasma etching, and an etching gasincludes a chlorine-based or fluorine-based gas.

In the process of adopting vacuum magnetron sputtering for MOsemiconductor materials, single-target sputtering or multi-targetco-sputtering may be adopted, and single-target sputtering is preferred.

This is because the single-target sputtering can implement a thin-filmwith better repeatability and stability, and the microstructure of thethin-film is easier to control. This is unlike a co-sputtering thin-filmin which sputtered particles are subjected to interference by morefactors in the process of recombination.

In the vacuum sputtering deposition process, a power supply may be radiofrequency (RF) sputtering, direct current (DC) sputtering or alternatingcurrent (AC) sputtering, and the AC sputtering commonly used in industryis preferred.

In the sputtering deposition process, the sputtering pressure may beselected from a range of 0.1-10 Pa, preferably 0.3-0.7 Pa.

When the sputtering pressure is excessively low, stable glow sputteringcannot be maintained. When the sputtering pressure is excessively high,the scattering and energy loss of sputtered particles in the process ofdeposition on a substrate 01 increase obviously, so that the kineticenergy decreases after the sputtered particles reach the substrate 01,and defects of formed thin-films increase, thereby seriously affectingthe performance of a device.

In the sputtering deposition process, the oxygen partial pressure isoptional in the range of 0-1 Pa, preferably 0.001-0.5 Pa, and morepreferably 0.01-0.1 Pa.

Oxygen partial pressure generally has a direct impact on the carrierconcentration of a thin-film in the process of preparing an oxidesemiconductor by sputtering, and some defects related to oxygenvacancies may be introduced. Excessively low oxygen content may causeserious oxygen mismatch and increase of carrier concentration in thethin-film, while excessively high oxygen vacancies may cause more weakbonds and reduce the reliability of the device.

In the sputtering deposition process, the substrate temperature ispreferably 200-300° C.

In the process of channel layer thin-film deposition, a certainsubstrate temperature can effectively improve the bonding mode ofsputtered particles after the sputtered particles reach the substrate01, thereby reducing the probability of occurrence of weak bonds, andimproving the stability of the device. Certainly, the same effect canalso be achieved by subsequent annealing treatment and other processes.

The thickness of the channel layer 03 is optional in the range of 2-100nm, preferably 5-50 nm, and more preferably 20-40 nm.

The materials of the source electrode and the drain electrode in thepresent invention are not particularly limited, and may be arbitrarilyselected from materials well known in the art on the premise that theimplementation of devices with various required structures is notaffected. For example, the materials are transparent conductive oxides(ITO, AZO, GZO, IZO, ITZO, FTO, etc.), metals (Mo, Al, Cu, Ag, Ti, Au,Ta, Cr, Ni, etc.) and alloys thereof, metals and oxides (ITO/Ag/ITO,IZO/Ag/ZO, etc.), and composite conductive thin-films formed by stackingmetals (Mo/Al/Mo, Ti/Al/Ti, etc.).

The methods for preparing thin-films of the source electrode and thedrain electrode may be sputtering, thermal evaporation and otherdeposition methods, and preferably sputtering deposition. Because thethin-films prepared by this method have good adhesion to a substrate 01and excellent uniformity, the thin-films can be prepared in a largearea.

Here, it should be noted that in the preparation of a device with aback-channel etch structure, the source electrode, the drain electrodeand the channel layer 03 need to have a proper etching selectivity,otherwise the device cannot be prepared. The etchant for wet etching inthe embodiment of the present invention is an etchant (such as hydrogenperoxide-based etchant) based on conventional metals in industry. Thisis mainly because the MO semiconductor material of the present inventioncan effectively resist the etching of the wet hydrogen peroxide-basedetchant, and has a high etching selectivity with metals (such asmolybdenum, molybdenum alloy, and molybdenum/aluminum/molybdenum). TheMO semiconductor layer is basically not affected by the etchant, and theprepared device has excellent performance and good stability. Inaddition, the dry etching in the embodiment of the present invention isbased on conventional etching gases (such as chlorine-based gases andfluorine-based gases) in industry, and has little impact on the oxidesemiconductor layer of the present invention, so the prepared device hasexcellent performance and good stability.

The materials of the passivation layer in the present invention are notparticularly limited, and may be arbitrarily selected from materialswell known in the art. For example, the materials are silicon oxide,silicon nitride, alumina, tantalum oxide, hafnium oxide, yttrium oxide,and polymer organic film layers.

It should be pointed out that the components of these insulatingthin-films may be inconsistent with a theoretical stoichiometric ratio.In addition, the insulating layer 04 may be formed by stacking variousinsulating films, which can implement better insulating characteristicsand improve the interface characteristics between the channel layer 03and the passivation layer. Moreover, the passivation layer may beprepared in various ways, such as physical vapor deposition, chemicalvapor deposition, atomic layer deposition, laser deposition, or asolution method.

The processing technology in the thin-film transistor preparationprocess implemented by the present invention is further described below.

Relatively, because of the participation of high-energy plasma, thedeposition rate of thin-films prepared by sputtering is generallyfaster. There is no enough time to perform the relaxation process of thethin-films during the deposition process. This may result in dislocationin a certain proportion and stress remaining in the thin-films. Thisrequires post heat annealing treatment to continue to achieve therequired relatively steady state and improve the properties of thethin-films.

In the implementation of the present invention, annealing treatment ismostly set after the deposition of the channel layer 03 and after thedeposition of the passivation layer. On the one hand, the annealingtreatment after the deposition of the channel layer 03 can effectivelyimprove in-situ defects in the channel layer 03 and improve the abilityof the channel layer 03 to resist possible damage in the subsequentprocess. On the other hand, in the subsequent passivation layerdeposition process, due to the participation of plasma and themodification of active groups, this may require an “activation” processto further eliminate the effects of an interface state, some donordoping, etc.

In addition, in the implementation of the present invention, thetreatment modes may include not only heating treatment, but also plasmatreatment interfaces (such as an insulating layer 04/semiconductorinterface and a channel layer 03/passivation layer interface).

The foregoing treatment processes can effectively improve theperformance and stability of the device.

The foregoing embodiments are preferred embodiments of the presentinvention. However, the embodiments of the present invention are notlimited by the foregoing embodiments. Any other changes, modifications,replacements, combinations and simplifications made without departingfrom the spirit and principle of the present invention should all beequivalent replacement manners, and fall within the protection scope ofthe present invention.

What is claimed is:
 1. A metal oxide (MO) semiconductor, wherein themetal oxide semiconductor is implemented by respectively doping at leastan oxide of rare earth element R and an oxide of rare earth element R′into an indium-containing metal oxide MO—In₂O₃ semiconductor to form anIn_(x)M_(y)R_(n) R′_(m)O_(z) semiconductor material, wherein x+y+m+n=1,0.4<x<0.9999, 0<y<0.3, 0.06<(m+n)<0.2, m>0, n>0, and z>0, wherein M isone selected from Zn, Ga, Sn, Ti, Zr, and Ta, or a combination of anytwo or more thereof, R is Eu or Yb, and R′ is Pr, or Ce or Dy.
 2. The MOsemiconductor of claim 1, wherein the MO semiconductor is prepared intoa film by adopting any one of a physical vapor deposition process, achemical vapor deposition process, an atomic layer deposition process, alaser deposition process, a Reactive-Plasma Deposition (RPD) process anda solution method.
 3. A thin-film transistor, comprising a gateelectrode, an active layer, an insulating layer located between the gateelectrode and the active layer, a source electrode and a drain electrodeelectrically connected to both ends of the active layer respectively,and a spacer layer, wherein the active layer is the MO semiconductor ofclaim
 1. 4. The thin-film transistor of claim 3, wherein the spacerlayer is one layer structure selected from a silicon oxide thin-film, asilicon nitride thin-film and a silicon oxynitride thin-film prepared byplasma-enhanced chemical vapor deposition or a laminated structurecomposed of any arbitrary two or more thereof.